The present invention relates to a centrifugal separator comprising a rotor body which forms a separation chamber and comprises two axially separated end walls and a surrounding wall situated axially between the end walls, a stack of conical separation discs arranged between the end walls in the separation chamber coaxially with the rotor, and a fastening means separate from the surrounding wall and arranged to keep the end walls and the stack of separation discs therebetween axially together. A centrifugal separator of this kind is described e.g. in U.S. Pat. No. 1,343,325.
As can be seen from U.S. Pat. No. 1,343,325 the two end walls of the known centrifugal separator are kept axially together by means of a central locking joint. This comprises a vertical column permanently connected with the lower end wall and extending centrally through the centrifuge rotor, and a looking ring threaded on to the column and retaining the upper end wall relative thereto. The surrounding wall of the rotor is formed in one piece with the upper end wall and is kept axially in sealing engagement with the lower end wall by means of the central locking joint. Centrifugal separators of this kind were common around the turn of the century when the centrifuge rotors were still relatively small.
When larger centrifuge rotors were developed and higher rotational speeds were used the demands on strength of the central locking joint were increased. As a consequence thereof another type of locking joint was developed. One example of such a locking joint is shown in U.S. Pat. No. 1,571,943. This locking joint comprises a locking ring dimensioned and arranged to keep the rotor end walls axially together in the area of the largest peripheries thereof instead of, as previously, centrally in the rotor. Thus, the locking ring has been given a substantially larger diameter than before, whereby its threads may take up correspondingly larger shearing forces.
A locking joint of the last mentioned type is more difficult to deal with than a central locking joint and, therefore, is not desirable in connection with relatively small centrifuge rotors.